1. Field of the Invention
This invention relates to a vehicle control apparatus and, in particular, to a vehicle control apparatus capable of transmitting and receiving a signal to and from a mobile device for permission authentication for use of a vehicle.
2. Description of Related Art
An electronic key system for a vehicle is known that is capable of transmitting and receiving a signal to and from a mobile device for permission authentication for use of the vehicle (see, for example, JP-A-2004-114860). In JP-A-2004-114860, after the engine is started, a request signal is transmitted from a vehicle-side transmitting circuit to an electronic key (mobile device) at predetermined intervals and a response signal is transmitted from the electronic key having received the request signal to a vehicle-side receiving circuit. Then, when the vehicle-side receiving circuit does not continuously receive response signals of a number larger than a specified number, there is a high possibility that the electronic key is not within a receivable range and there is a high possibility that a driver has dropped the electronic key, so the system lights an alarm light in order to let the driver know that he has dropped the electronic key. With this, it is possible to prevent the driver from losing a dropped electronic key.
However, in JP-A-2004-114860, after the engine is started, the request signal is transmitted at predetermined intervals from the vehicle-side transmitting circuit to the electronic key and the response signal is transmitted from the electronic key having received the request signal to the vehicle-side receiving circuit, so the request signal and the response signal are transmitted and received even when the vehicle is in a stop state. Here, also when the driver has dropped the electronic key in the case where the vehicle is substantially in the stop state, there is a high possibility that the electronic key will be located within a transmittable range near the vehicle, so there is a high possibility that the request signal and the response signal will be transmitted and received. For this reason, when the vehicle is substantially in the stop state, it is difficult to inform the driver that the electronic key has been dropped, so the need for conducting the communications between the vehicle-side transmitting circuit and receiving circuit and the electronic key is low. In this manner, in JP-A-2004-114860, even when the need for conducting the communications between the vehicle-side transmitting circuit and receiving circuit and the electronic key is low, the request signal and the response signal are transmitted and received at specified intervals. Thus, consumption of the battery of the electronic key is not suppressed.